Iron(II), Cobalt(II), Nickel(II), and Zinc(II) Silylene Complexes: Reaction of the Silylene [iPrNC(NiPr )NiPr] Si with FeBr , CoBr , NiBr ⋅MeOCH CH OMe, ZnCl , and ZnBr.

Reaction of the donor-stabilized silylene [iPrNC(NiPr )NiPr] Si (1) with FeBr , CoBr , NiBr ⋅MeOCH CH OMe, ZnCl , and ZnBr afforded the respective transition-metal silylene complexes 4-8, the formation of which can be described in terms of a Lewis acid/base reaction (4, 5, 7, 8) or a nucleophilic substitution reaction (6). However, the reactivity profile of silylene 1 is not only based on its strong Lewis base character; the different coordination modes of the two guanidinato ligands (4-6 vs. 7 and 8) add an additional reactivity facet. The paramagnetic compounds 4 and 5 and the diamagnetic compounds 6⋅THF, 7, and 8⋅0.5 Et O were structurally characterized by single-crystal X-ray diffraction. In addition, compound 6⋅THF was studied by N and Si solid-state NMR spectroscopy, and 7 and 8 were characterized by NMR spectroscopic studies in the solid state ( N, Si) and in solution ( H, C, Si). Compounds 4-8 represent very rare examples of Fe , Co , Ni , and Zn silylene complexes. Four-coordinate silicon(II) compounds with an SiN M skeleton (M=Fe, Co, Ni) and M in the formal oxidation state +2 (4-6) have not yet been reported, and five-coordinate silicon(II) compounds with an SiN Zn skeleton (7, 8) are also unprecedented.